Most steering columns rise when a vehicle is involved in a frontal impact. In other words, the steering column which normally is inclined upwardly and rearwardly at a predetermined angle, will rise to a greater angle upon frontal impact. This is caused by the vehicle engine being thrust rearwardly.
The rise in the steering column places the steering wheel/air bag assembly in an unfavorable position with respect to the driver's chest. When the-driver's chest comes in contact with the steering wheel/air bag assembly, the force against this assembly has a considerable off-axis bending component which is increased due to the rise in the steering column. If the rise in the steering column is such that the off-axis component of force on the steering wheel/air bag assembly acts above the center of mass of the driver's chest, then the driver tends to "submarine" or dive under the steering wheel, creating an even less favorable situation.
The steering column of this invention has a cross member or bracket which mounts the steering column to the vehicle frame. This bracket is slotted and notched to reduce its resistance to bending. When the steering column tilts up in a front end collision, the force of the driver upon being thrown forward against the steering wheel/air bag assembly will cause the bracket to bend and the steering column to tilt upwardly further. As a result, energy is absorbed and the impact on the driver is reduced.
Further in accordance with the invention, the steering column is made in two sections, an upper section and a lower section. The upper section is adapted to incline further upwardly when the driver is thrown forward against the steering wheel/air bag assembly. An energy absorbing device resisting and retarding such further upward inclination of the upper section is provided to reduce the impact on the driver.
As shown in certain specific embodiments about to be described, this energy absorbing device may take the form of a pair of plates held together under pressure in frictional sliding contact, or a strap of relatively stiff bendable material curved preferably either to arcuate or sinuous form and capable of opening up under stress. These energy absorbing devices retard and resist any further upward inclination of the upper section relative to the lower section and thereby reduce the reaction force or impact on the driver. The cross member or bracket which mounts the steering column to the frame preferably is secured to the lower section of the steering column and has a bendable flange connected to the upper section which resists and retards upward inclination of the upper section to further reduce the reaction force on the driver when his chest hits the steering wheel.
It is an object of this invention to provide a steering column energy absorbing assembly having the foregoing features.
Other objects are to provide a steering column energy absorbing assembly which is rugged and durable in use, composed of a relatively few simple parts, and capable of being readily and inexpensively manufactured.
Other objects, features and advantages of the invention will become more apparent as the following description proceeds, especially when considered with the accompanying drawings.